

A072406


Number of values of k for which C(n,k)C(n2,k1) is odd.


1



1, 2, 3, 2, 4, 4, 6, 4, 6, 8, 6, 4, 8, 8, 12, 8, 10, 16, 6, 4, 8, 8, 12, 8, 12, 16, 12, 8, 16, 16, 24, 16, 18, 32, 6, 4, 8, 8, 12, 8, 12, 16, 12, 8, 16, 16, 24, 16, 20, 32, 12, 8, 16, 16, 24, 16, 24, 32, 24, 16, 32, 32, 48, 32, 34, 64, 6, 4, 8, 8, 12, 8, 12, 16, 12, 8, 16, 16, 24, 16
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

0,2


LINKS

Table of n, a(n) for n=0..79.


FORMULA

If 2*2^m+1<n<=3*2^m+1 then a(n)=a(n2^m) except that a(3*2^m)=a(2^m)+2; if 3*2^m+1<n<=4*2^m+1 then a(n)=2*a(n2^m) except that a(4*2^m)=2*a(3*2^m)6. So a(2^m)=2^(m1)+2, a(2^m+1)=2^m, a(2^m+2)=6, a(2^m+3)=4, a(3*2^m)=2^m+4, a(3*2^m+1)=2^(m+1), a(3*2^m+2)=12, a(3*2^m+3)=8, etc. for m large enough to avoid confusion.


EXAMPLE

a(5)=4 since the values of C(5,k)C(3,k1) are 10, 51, 103, 103, 51, 10, i.e. 1,4,7,7,4,1 of which 4 are odd.


CROSSREFS

Cf. A001316, A072405.
Cf. A094959.
Sequence in context: A029143 A153846 A284383 * A297117 A120680 A071494
Adjacent sequences: A072403 A072404 A072405 * A072407 A072408 A072409


KEYWORD

nonn


AUTHOR

Henry Bottomley, Jun 16 2002


STATUS

approved



